1. Field of the Invention
The present invention relates to seed meters in which a seed disk is rotatably mounted within the meter housing, and more particularly to methods and apparatus for rotatably positioning a rotatably mounted seed disk at a desired location within the housing of a seed meter.
2. History of the Prior Art
It is known in the field of agricultural equipment and machinery to provide seed meters which meter or dispense individual seeds into a furrow in the ground at a controlled rate in conjunction with associated apparatus for creating the furrow and then moving loose soil back into the furrow after the seeds have been deposited therein. There are various different types of seed meters including the mechanical type in which individual seeds are plucked from a seed mass and discharged from the meter for deposit within the furrow by mechanical devices. Still other types of seed meters are of the air type in which a pressure differential is employed, typically in conjunction with a rotating seed disk or similar device, to pick up seeds from the seed mass and then discharge them from the meter into the furrow. Air seed meters can be of the positive air flow type in which the seeds are picked up by the seed disk and held thereon by blowing air. Air seed meters can also be of the vacuum type in which a reduced pressure is communicated to the seed disk in a manner enabling the disk to pick up and carry individual seeds thereon with the assistance of the reduced pressure.
An example of a vacuum seed meter is provided by a co-pending application, Ser. No. 546,834, abandoned, Lundie et al, filed Oct. 31, 1983 and commonly assigned with the present application. The Lundie et al application describes a vacuum seed meter in which a rotating seed disk is mounted within the hollow interior of a housing so as to have a seed mass disposed on one side thereof and a source of reduced pressure coupled to a vacuum chamber at the opposite side of the disk. The reduced pressure communicates with a plurality of seed cells recessed in the side of the disk facing the seed mass via apertures extending through the thickness of the disk from the bottoms of the cells. The reduced pressure assists the cells in picking up individual seeds from the mass and transporting them to a seed discharge area sealed off from the reduced pressure to provide for release of the seeds carried in the seed cells. The released seeds fall through a discharge chute into a furrow in the ground formed by an opener unit mounted in conjunction with the seed meter.
In the vacuum seed meter described in the Lundie et al application the seed mass on one side of the rotating seed disk is formed by seeds falling from a hopper mounted above the seed meter into a seed chamber formed at the side of the seed disk by the shape of the hollow interior of the meter housing. The outer peripheral portion of the seed disk is disposed closely adjacent an outer peripheral portion of the hollow interior of the meter housing to prevent seeds in the seed chamber from escaping to the outside of the seed meter.
A co-pending application, Ser. No. 546,829, now U.S. Pat. No. 4,613,056, Olson, filed Oct. 31, 1983 and commonly assigned with the present application, describes an arrangement of the vacuum seed meter of the Lundie et al application in which a relatively small space is formed between the outer peripheral portion of the seed disk and the adjacent peripheral portion of the hollow interior of the housing on the side of the seed disk where the seed mass resides. The space defines a gap between the seed disk and the housing which is large enough to permit expulsion of debris from the interior of the meter housing while at the same time preventing the escape of the seeds themselves including in particular seeds of relatively small size. The debris which is eliminated by passing through such gap includes dust, dirt and unwanted particles of relatively small size such as broken seed particles or chips and the like. As described in the Olson application the outer peripheral portion of the seed disk may be provided with a succession of fins disposed on the opposite sides of recesses therebetween to agitate and encourage the expulsion of debris which may accumulate at the interface between the seed disk and adjacent portions of the housing interior.
In the arrangement described in the Olson application, it is desirable not only that the gap between the seed disk and the housing interior be of desired nominal size but also that such gap be of relatively uniform size about the entire outer peripheral portion of the seed disk. A gap which is too large may result in expulsion of the seeds themselves, particularly those seeds of smaller size, in addition to the debris. Conversely, a gap which is too small may not allow proper expulsion of the debris. A non-uniform gap tends to provide non-uniform expulsion of debris and the unwanted expulsion of seeds at locations where the gap becomes unduly large.
In the particular vacuum seed meters described in the Lundie et al and Olson applications, the seed disk is mounted for rotation within the hollow interior of the meter housing by a shaft rotatably mounted within the housing and having a seed disk mounting hub disposed on the outer end thereof so as to mount the seed disk for rotation with the shaft. An example of the seed disk mounting hub is provided by a co-pending application, Ser. No. 546,831, now abandoned, Webber, filed Oct. 31, 1983 and commonly assigned with the present application. During manufacture of such seed meters, the seed disk mounting hub is typically mounted on the outer end of the shaft such as by a cotter pin, following which the opposite end of the shaft is pressed into the outer race of a bearing within the housing to achieve an interference fit therebetween. The pressing of the shaft into the bearing race is carried out using equipment which has been programmed to provide a desired gap between the seed disk and the housing. Unfortunately, this process makes it difficult to form such gap within the close tolerances desired. Moreover, once the shaft is pressed into the bearing race, it can be very difficult to relocate the shaft to provide desired disk-housing spacing, particularly where the shaft installation equipment is not available. Such a problem may arise, for example, in the field where the farmer discovers that the gap between the seed disk and the housing is too large or too small. Another problem which commonly exists is lack of perpendicularlity. As a result of misalignment of the shaft upon pressing into the bearing race, or possibly due to other factors, the central axis of the shaft and thus of the seed disk itself may not be precisely perpendicular to the plane of the peripheral portion of the housing interior which interfaces with the outer peripheral portion of the seed disk. This may result in a non-uniform gap with its attendant disadvantages as previously noted.
Accordingly, it would be advantageous to provide an improved method and apparatus for rotatably mounting a seed disk within the hollow interior of a housing of a seed meter.
It would furthermore be advantageous to provide an improved method and apparatus for rotatably mounting a seed disk within the hollow interior of a housing of a seed meter in a manner which provides both a gap of desired size therebetween and a gap which is relatively uniform in size about the entire outer peripheral portion of the seed disk.